Blood clots (emboli) carried in the blood stream often constitute serious threats to health and in some instances, to life itself. The reduction of such clots, or their stabilization and arrest of further migration in the circulatory system of the body, is desiderata constantly motivating the development by the medical profession of new techniques and devices for this purpose. Although emboli moving in other portions of the circulatory system can also present serious problems, development of means for preventing emboli from migrating into the pulmonary circulation from the vena cava has received the primary attention.
One method of capturing emboli is the utilization of filters emplaced in the major blood vessels such as the vena cava. U.S. Pat. No. 4,817,600 to Herms et al. discloses a titanium filter having a plurality of legs joined to a head or nose bead; the legs having a first straight portion, and sharply divergent legs extending therefrom.